FR2470167A1 - Recovery of titanium values in high yield - by reductive roast and hydrogen halide leach - Google Patents

Abstract

Ti values are recovered by roasting, the crushed source e.g. ilmenite at 600-1000 degrees C in presence of H2 and/or CO gas, leaching with hydrogen halide at up to 110 degrees C sepg. gangue and cooling solubilised metal halides to ppts. FeCl2. The leach liquor is then treated at 70-100 degrees C with 2.5-50 times stoichiometrically required amount of Fe2O3 to convert Ti halide to TiO2. The leach liquor is agitated and solids are recovered and mixed with a second leach soln. contg. sufficient Ti halide to consume remaining Fe2O3. TiO2 is recovered. The ore e.g. ilmenite is crushed to -35 mesh and roasted at 600-900 degrees C in a 50-50 CO-H2 gas mixt. for 0.25-2 hours., then leached with HCl at 80-100 degrees C for 0.25-1 hour. The leach liquor is cooled to 0-90 degrees C to cause crystillisation of FeCl. The excess of Fe2O3 is then added and reaction allowed to proceed for 1-10 minutes after which solids are removed and mixed with the second leach solution.

Description

Titanium in metallic form or in form of a compound
is an important element in the chemical series. For example, titanium dioxide is used in paint pigments, rubbers and white plastics,
floors, glass and ceramic articles, inks for paints, as an opacifying agent for papers, etc. The other titanium compounds are used in electronics, as flame retardants, as water-repellent agents, etc. .. The metal can be used as such or in the form of an alloy as a structural material in aeronautics, in jet engines, in marine equipment, in the textile industry, in surgical instruments, in orthopedic prostheses, in sports equipment, in food handling equipment, etc. So far, in the recovery of titanium from titanium sources such as ilmenite, rutile, etc., titanium was subjected to separation steps which involved the formation of titanium as a compound under valence state of +4, such compounds generally relating to titanium oxides. However, when attempting to separate the titanium dioxide from impurities that are also contained in the ore, such as iron, the hydrolysis of titanium dioxide at elevated temperatures generally also leads to relatively large amounts being obtained. iron simultaneously with titanium.

 So far in the prior art, various methods have been used to recover titanium from titanium sources. For example, in U.S. Patent No. 3,236,596, a non-roasted dithmenite ore is leached with hydrogen chloride at an elevated temperature, after which the dissolved iron is reduced with the aid of iron or other reducing agents for precipitating the ferrous chloride by saturating the liquor with gaseous hydrogen chloride, the hydrogen chloride is then removed from the liquor by vacuum distillation and the titanium is recovered by conventional means. Also, in U.S. Patent No. 3,825,419, an ilmenite ore is reduced to produce ferrous oxides. The reduced ore is then leached for about 4 hours under moderate pressure to dissolve the iron in the acid. same time as about 15% titanium. The iron is recovered as ferric oxide containing impurities in a spray roasting device, while the insoluble product which is essentially titanium dioxide, but which contains all of the silica present in the original ore, is recovered. U.S. Patent No. 3,859,077 also discloses a titanium recovery process in which a titanium tetrahalide is mixed with iron oxide contained in slag or titaniferous ore at an extremely high temperature of about 1000 ° C. C, to produce volatile impurity chlorides and titanium dioxide. A similar patent, US Patent No. 3,929,962, also discloses a reduction of a high temperature titanium source to produce a titanium sesquioxide. which is in a form easy to treat for titanium-iron separation Another prior document, US Pat. No. 3,903,239, discloses a process for recovering titanium in which ungrilled ilmenite is leached for a period of several days at room temperature to recover about 80% of the titanium.

Sulfur dioxide is added during leaching to precipitate the ferrous chloride, and the titanium dioxide is recovered by diluting and heating the solution.

 As will be demonstrated in more detail below, the Applicant has now discovered that improved titanium dioxide yields can be achieved by treating titanium halides in a particular manner.

 The present invention relates to a process for obtaining titanium compounds such as titanium dioxide with excellent yields. More particularly, the present invention relates to a process for recovering metallic titanium with economical yields from a titanium source such as ilmenite. By using the process according to the invention, it is possible to obtain an excellent yield of metallic titanium by using relatively poor ores as starting materials.

 The object of the present invention is to provide an improved process for the production of metallic titanium.

 It is also intended to provide a hydrometallic process for obtaining titanium with high yields in the form of rutile from titanium sources such as ilmenite.

 According to one embodiment, the present invention resides in a process for producing titanium from a titanium source which comprises grinding the titanium source, subjecting the ground source to a reducing roasting at high temperature in a reducing medium , leaching the reduced source with a leach solution comprising a halogen-containing compound, separating the insoluble material from the rich leach liquor containing titanium halides, treating the leach liquor to precipitate the bioxide of titanium, and recovering the titanium dioxide, this process being characterized in that it consists in treating the leach liquor with the aid of an excess of ferric oxide while maintaining a stirring of the solution, to be recovered the solids formed by the ferric oxide treatment of the titanium halide and mixing these solids with a second leach solution in order to consume the remaining ferric oxide and recovering the resulting titanium dioxide.

 A specific embodiment of the present invention resides in a process for preparing titanium from ilmenite which comprises comminuting the ilmenite to a suitable particle size, subjecting the milled ilmenite to a reducing roaster at a temperature of about 600 to 1000 ° C, in a reducing medium comprising a mixture of carbon monoxide and hydrogen, to leach the reduced source with an aqueous solution of hydrogen chloride, separating the insoluble material rich leach liquor, cooling the leach liquor to precipitate the ferrous chloride and separating the ferrous chloride from the leach liquor, treating the leach liquor with an excess of ferric oxide of about 2.5 to 50 times the stoichiometric amount required to react with the titanium chloride, to remove the solids that form during the ferric oxide treatment, to mix the solids with a second leach solution to consume the remaining ferric oxide, and recover the desired titanium dioxide.

Other features and advantages of the present invention
will be better understood from reading the detailed description of the present invention, which follows.

As previously described, the present invention relates to a process for the preparation of rutile, easy to obtain, from a leach liquor containing soluble titanium halides. The process for obtaining the desired metal titanium is carried out by grinding a mineral source such as ilmenite or other sources such as sand, which contains the desired metal, mainly titanium, as well as amounts of other metals. such as iron, vanadium, chromium, manganese, etc., at a particle size which is less than about 0.50 mm. The comminuted metal source is then subjected to reductive roasting at high temperature ranging from about 600 to 10,000 C or more, and preferably from about 600 to about 9,000 C, in the presence of a reducing gas such as hydrogen, carbon monoxide, and combinations of carbon monoxide and hydrogen, etc., or other suitable reducing agents. The reducing roasting is carried out for a period of about 0.5 to 2 hours or more. In the preferred embodiment of the present invention, the reducing atmosphere which is used for roasting usually comprises a mixture of about 50% carbon monoxide and 50% hydrogen, an excess of reducing agent being used to completely reduce the iron that is present in the system, metal. It is also within the scope of the present invention that the ground ore may, if necessary, be subjected to oxidative roasting before reducing roasting, this oxidizing mesh being produced at a temperature of approximately 600 to 900 ° C.
C, in the presence of an oxidizing atmosphere that is provided by the presence of air or oxygen. However, this step is not necessarily present in the process of the present invention. Following the reductive roasting of the metal source, this source is then leached with an aqueous solution of sodium halide. which, in the preferred embodiment of the invention, is an aqueous solution of hydrogen chloride / although other hydrogen halides such as hydrogen bromide and hydrogen iodide may also between used, but not necessarily with equivalent results. The previous leaching of the metal source is usually carried out at a temperature which can range from room temperature to about 110 ° C, the preferred temperature range being from about 80 to 100 ° C, for a period of 0.25 hours. up to an hour or more.

 After leaching the metal source which forms iron halides and soluble titanium halides such as ferrous chloride, titanium trichloride, etc., the mixture is subjected to a separation step in which the solid gangue is separated from soluble metal chlorides, and discarded. Separation of the solid gangue from soluble metal chlorides can be carried out in any suitable manner by means well known in the art, said means including decantation, filtration, etc.

According to one embodiment of the process of the present invention, the soluble metal halides can then be cooled to a temperature sufficient to achieve crystallization or precipitation of the ferrous chloride. For example, the temperature at which crystallization or precipitation of ferrous chloride is obtained can range from about 0 to a temperature slightly above room temperature or at temperatures as high as 90 ° C in extreme cases. temperatures below room temperature are used, the cooled solution is maintained at this temperature value below room temperature by external means such as an ice bath, a cooling coil, etc.
After completion of the crystallization of the ferrous chloride, the solids are separated from the dissolved titanium chloride, such as titanium trichloride, by conventional means such as filtration, decantation, etc.

The desired titanium dioxide in the form of rutile is obtained by treating the resulting leach solution, containing the aqueous titanium trichloride with a metal oxide, and preferably, iron oxide, such as ferric oxide. This latter compound can be obtained by oxidizing the solid ferrous chloride which has been separated and recovered from the
leachate solution in any manner known in the art.

For example, the ferrous chloride may be oxidized at temperatures of about 300 to 800 ° C by contact with an oxygen-containing gas such as air or oxygen so that the ferrous chlorides are Ferric oxide and ferric oxide, the latter being the predominant form of iron oxide.The treatment of the titanium trichloride-containing leach solution to generate the hydrolysis reaction is accomplished by adding the material containing the To obtain effective nucleation of rutile, it has been found that the amount of iron oxide that is used must be present in a large excess, and preferably present in a large amount. amount of about 2.5 to 50 times the stoichiometric amount that is required to react with the titanium halide such as titanium trichloride.The large excess is added to the charged leach liquor while maintaining agitation of the solution.

 After allowing the reaction to proceed for a period of time ranging from one to ten minutes or more, the solid materials that are formed are removed from the solution and then mixed with a second leach solution that contains a sufficient amount of halide. of titanium to react completely with the iron oxide remaining in the solids.The reaction of the ferric oxide with the titanium compound is carried out at elevated temperatures which can range from about 70 to 100 ° C or higher and, preferably from about 75 to 95 ° C. Following the second reaction, the solids can be recovered by separating the depleted leach liquor which contains ferrous chloride and recovered by conventional means or, if desired, the titanium dioxide can be further processed to recover the metallic titanium.

 If desired, the process can also be carried out in a different manner by treating the rich leach liquor containing the soluble metal halides which have been separated from the insoluble gangue by using excess ferric oxide in an amount as set forth herein. above in more detail. At the end of the nucleation and precipitation of the two-stage titanium compound, as described above, the solids which comprise the titanium dioxide are then separated from the liquid.

Following the separation, the liquid is then cooled to a temperature within the range indicated above, in order to achieve crystallization of the ferrous chloride. The solid ferrous chloride may then be treated either by a direct reduction step to form metallic iron and hydrogen chloride or, if desired, it may be subjected to an oxidation step by treatment with the aid of gas containing air or oxygen at a temperature of about 300 to 800 ° C to form ferric oxide. The ferric oxide can then be recycled to the step wherein the rich leach liquor is contacted with excess ferric oxide to form the desired titanium dioxide.

 The process of the present invention may be carried out in any suitable manner and may comprise either continuous operation or batch operation. For example, according to one embodiment of the method, when batch operation is performed, the titanium-containing source, which has been milled or crushed to the desired particle size, usually about 0.50 to less than of 0, 149 mm, is placed in an apparatus such as an oven in which it is roasted at a temperature within the range indicated above, while subjecting the ore to a reducing atmosphere such as a mixture of oxide After completion of the reductive roasting, the milled ore is then placed in a second vessel in which it is subjected to a leaching operation by contact with aqueous hydrogen chloride such as hydrochloric acid. concentrate, while the temperature is maintained between about 80 and 105 ° C. After completion of the desired leaching operation, the solid material such as gangue and / or metal compounds insolubles are separated from the rich leach liquor which is then recovered. A process for treating the rich leach liquor then comprises placing the leach liquor in a tank or other such apparatus which is then cooled or maintained at a relatively cool temperature to crystallize the ferrous chloride. precipitation of the ferrous chloride, the leach liquor containing the soluble titanium chloride is separated from the solid ferrous chloride by conventional means such as filtration, centrifugation, etc ..., and placed in another apparatus or it is put in contact with a excess of ferric oxide in order to carry out the operation which has already been described above.

The apparatus which is used for the ferric oxide treatment is provided with means of heating as well as agitation which allow agitation of the mixture by means of mechanical stirrers or other means in order to keep the solution in a state agitated during the nucleation period which can range from one to ten minutes or more. After completion of the desired nucleation period and concomitant titanium dioxide formation, the solids are separated and contacted with a second quantity of titanium chloride-containing leach liquor to consume the remaining amount of ferric oxide which is present.

The solid titanium dioxide is then separated from the soluble iron chloride that formed during the reaction, and is recovered.

 Alternatively, if desired, the rich leach liquor after recovery following the separation of the insoluble gangue can be treated at elevated temperature with ferric oxide prior to the removal of the ferrous chloride present in the liquor. lixiviation with titanium chloride After treatment of the leach liquor with excess ferric oxide, in a manner similar to that described above, the solid titanium dioxide is recovered while the soluble ferric chloride initially present in the leach liquor and the additional ferric chloride which is formed by the reaction between ferric oxide and titanium chloride, can then be precipitated by cooling the liquor to form solid ferrous chloride. Ferrous chloride can then be treated either by a reduction step or by an oxidation step. If this first step is carried out, namely, the direct reduction of ferrous chloride by treatment with hydrogen at elevated temperature, the resulting metallic iron that is formed can be recovered while the hydrogen chloride can be recycled. to the leach liquor.

Alternatively, when the ferrous chloride is subjected to an oxidation step by treatment with a gas containing oxygen or oxygen, at elevated temperature, the ferric oxide that forms can be recycled to the recovery of titanium dioxide, ferric oxide acts
as a nucleating agent
It is also within the scope of the present invention that the process is carried out in continuous operation.

When such a type of operation is used, the ore that has been milled or crushed to the desired particle size is introduced into a
apparatus such as an oven at a predetermined speed, while it is subjected to the action of a reducing atmosphere such as hydrogen or
combination of carbon monoxide and hydrogen and that the temperature
is maintained in the furnace at about 600 to 1000 ° C. After completion of the passage in the furnace, the reduced ore is continuously charged into the leaching zone in which it is brought into contact with a furnace.
aqueous leaching solution comprising a hydrogen halide such as hydrogen chloride and after passing through the leaching zone which is maintained at an elevated temperature within the range set forth above, the solution containing the metal chlorides solublestel which In one embodiment, the rich leach liquor is then continuously charged to a crystallization zone which is maintained at a lower temperature to facilitate precipitation or precipitation. The crystallization of the ferrous chloride The leach liquor containing the soluble titanium chloride is withdrawn continuously from this zone and introduced into a precipitation zone in which it is brought into contact with an excess of ferric oxide while the solution is maintained in an agitated state.Solid materials including excess ferric oxide and bioxide of titanium, are separated from the resulting soluble ferrous chloride and contacted with a second leach liquor containing soluble titanium chloride to consume the excess ferric oxide supra. The solid materials that result from this second treatment and which include the titrant dioxide, are recovered and processed in a conventional manner. The ferrous chloride which has been separated from the leachate may, if desired, be introduced into an oxidation zone in which it is contacted with an oxygen-containing gas at a high temperature of about 300. at 800 ° C, to form ferric oxide, which compound is then used to treat the leach liquor containing the insoluble titanium chloride, while the hydrogen chloride which forms during this oxidation reaction is recycled to the leaching zone to form part of the leach solution load.

 Alternatively, the rich leach liquor which has been separated from the solid gangue may be treated with ferric oxide before the ferrous chloride has been precipitated. The contact with the ferric oxide is carried out in a manner analogous to that indicated above and, following this contact, solid titanium dioxide is formed and withdrawn continuously and recovered. The soluble ferrous chloride solution which at this stage contains an additional amount of ferrous chloride due to its formation during the precipitation of the titanium dioxide, is crystallized by continuously passing through a crystallization zone which is The solid ferrous chloride can then be continuously recovered from this crystallization zone and treated either by a direct reduction step or by an oxidation step to provide the desired metal iron and optionally ferric oxide, if desired.

 The following example is given for purposes of illustrating the process of the present invention.

EXAMPLE
A Canadian ilmenite ore is coarsely milled in a mill at a particle size of less than 0.230 mm and roasted for one hour at 750 ° C in a stream of 650 ml per minute of hydrogen and carbon. 650 ml per minute of carbon monoxide At the end of this roasting time, 50 g of reduced ore is mixed with 300 ml of hydrochloric acid and heated to a temperature of 100 ° C. The ore is leached at this temperature for a period of 15 minutes and then the solution is filtered. After filtration, the filtrate is cooled to room temperature to precipitate the ferrous chloride. The solid materials that are recovered are washed and dried. Following this step, 100 ml of liquid which is analyzed and contains 25 g / l of iron. 49 g / l of titanium and 0.42 g / l of vanadium are heated to 80 ° C. and a large excess of ferric oxide in an amount of 26.0 g is added with stirring of the solution. during a period of 5 minutes with stirring, then the solid materials are recovered by filtration, washed, dried and crushed to a size less than 0.177 mm.mm Analysis of this liquid indicates the presence of 150 g / l of iron and only 0> 12 g / l of titanium, which corresponds to a titanium recovery of 99.8%.

The solid materials that result from the first reaction are then added to a new 100 ml portion of the solution recovered from the ferrous chloride separation. The solution is stirred again and reacted for 5 minutes at 80 ° C. At the end of this period, the solution is again filtered and the solid materials washed and dried.

The solid materials which correspond to 12.58 g of rutile containing secondary proportions of iron, magenium, vanadium, and cobalt are recovered. It should be noted, as previously indicated, that the first treatment with an excess of ferric oxide led to a recovery of titanium of 99.8%, whereas the second reaction of titanium dioxide containing ferric oxide unreacted with the solution containing the titanium chloride, leads to a 66% recovery of titanium for a total recovery of 84%.

 An analogous test in which only a slight excess of ferric oxide was added to a titanium chloride liquor in a one-step precipitation process produced no rutile precipitates. The advantage resulting from this process therefore appears clearly.

Claims (9)

 A process for producing titanium from a source containing titanium, comprising  a) grinding the source containing titanium;  b) subjecting the milled source to a reducing roaster at elevated temperature in a reducing medium;  c) leaching the reduced source with a leach solution containing a halogen-containing compound;  d) separating the insoluble materials from the rich leach liquor containing titanium halides;  e) treating the leach liquor to precipitate the titanium dioxide, and  f) recovering the titanium dioxide; characterized by treating the leach liquor with an excess of ferric oxide while maintaining the stirred solution, recovering the solid materials formed by the ferric oxide treatment, the titanium halide and mixing these solid materials with a second leach solution to consume the remaining ferric oxide and to recover the resulting titanium dioxide  2. Method according to claim 1, characterized in that the excess of ferric oxide is between about 2.5 and 50 times the stoichiometric amount necessary to react with the titanium halide.  3. Method according to claim 1 or 2, characterized in that the precipitation of titanium dioxide by addition of ferric oxide is carried out at a temperature of about 70 to 100 ° C.  4. Method according to any one of the preceding claims, characterized in that the treatment of the leach liquor with the aid of ferric oxide is carried out for a period of time of about one to ten minutes.  5. Process according to claim 1, characterized in that the reducing roasting is carried out at a temperature of about 600 to 1000 ° C.  6. Process according to any one of claims 1 to 5, characterized in that the reducing medium is hydrogen.  7. Method according to any one of claims 1 to 5, characterized in that the reducing medium is a mixture of hydrogen and carbon monoxide.  8. Process according to any one of claims 1 to 7, characterized in that the leaching of the reduced source is carried out at a temperature ranging from room temperature to approximately 110 ° C.  9. Process according to any one of claims 1 to 8, characterized in that the compound containing a halogen in the leaching solution is hydrogen chloride.